ospfv3: fix: dispatch the BackupSeen event computed from received Hellos

processHelloPacket correctly computed backupSeen per RFC 2328 Section 9.5 --
the neighbor declares itself Backup Designated Router, or declares itself
Designated Router with no Backup, while this interface is in Waiting -- but
then discarded the flag ((void)backupSeen). A router joining a broadcast
segment with an already-established DR therefore always sat out the full
40s wait timer instead of ending Waiting immediately. Dispatch
BACKUP_SEEN_EVENT to the interface FSM like OSPFv2's HelloHandler does.

All 11 ospfv3 + BgpAndOspfv3 fingerprints are byte-identical: in the shipped
examples all routers start synchronized, so every interface leaves Waiting via
the wait timer before any DR is established, and the reconnect scenarios
rejoin two-router segments whose DR state was reset. The event matters for
staggered starts (startupTime) and for routers joining live segments.

Author: avarga

src/inet/routing/ospfv3/interface/Ospfv3Interface.cc

@@ -304,7 +304,6 @@ void Ospfv3Interface::processHelloPacket(Packet *packet)
     const auto& hello = packet->peekAtFront<Ospfv3HelloPacket>();
     bool neighborChanged = false;
     bool backupSeen = false;
-    (void)backupSeen; // FIXME set but not used variable
     bool neighborsDRStateChanged = false;
     bool drChanged = false;
     bool shouldRebuildRoutingTable = false;
@@ -525,6 +524,11 @@ void Ospfv3Interface::processHelloPacket(Packet *packet)
                 neighbor->processEvent(Ospfv3Neighbor::ONEWAY_RECEIVED);
             }
 
+            if (backupSeen) {
+                EV_DEBUG << "Backup Designated Router seen in Hello packet\n";
+                this->processEvent(Ospfv3InterfaceEvent::BACKUP_SEEN_EVENT);
+            }
+
             if (neighborChanged) {
                 EV_DEBUG << "Neighbor change noted in Hello packet\n";
                 this->processEvent(Ospfv3InterfaceEvent::NEIGHBOR_CHANGE_EVENT);